Master2 TSM January 2009
TD2: Use Cases and State Machines
1 ATM Specifications
ATM = Automatic Teller Machine
ATM offers the following services:
1. Distribution of money to every holder of a smartcard via a card reader and a cash dispenser.
2. Report of account balance, cash and checks deposit facilities for bank customers who hold a smartcard from their bank.
3. All transactions are made sure.
4. The dispenser has to be refilled from time to time.
Abbreviations used in this text:
• CardHolder = Visa Card holder
• BankCustomer = Bank customer who holds a smartcard from his/her bank
• VisaAS = Visa Authorization System
• BankIS = Bank Information System
2 Example of Use Case Specification
2.1 Withdraw money using a Visa card
Summary: This use case allows a Visa card holder, who is not a customer of the bank to withdraw money if his/her daily limit allows it.
1. The Visa CardHolder inserts his/her smart card in the ATM’s card reader.
2. The ATM verifies that the card that has been inserted is a smartcard.
3. The ATM asks the Visa CardHolder to enter his/her pin number.
4. The Visa CardHolder enters his/her pin number.
5. The ATM compares the pin number with the one that is encoded on the chip of the smartcard.
6. The ATM requests an authorization from the Visa authorization system
7. The Visa authorization system confirms its agreement and indicates the daily withdrawal limit.
8. The ATM asks the Visa CardHolder to enter the desired withdrawal amount.
9. The Visa CardHolder enters the desired withdrawal amount.
10. The ATM checks the amount against the daily withdrawal limit.
11. The ATM asks the Visa CardHolder if he/she would like a receipt.
12. The Visa CardHolder requests a receipt.
13. The ATM returns the card to the Visa CardHolder.
14. The Visa CardHolder takes his/her card.
15. The ATM issues the banknotes and a receipt.
16.
The Visa CardHolder takes the banknotes and the receipt.Variations: Temporarily incorrect pin number
• At step 5, the Visa CardHolder fails to enter a correct pin number
• 6. The ATM informs the CardHolder that the pin is incorrect for the first or second time.
• 7. The ATM records the failure on the smartcard.
• The scenario goes back to step 3.
Variations: The amount requested is greater than the daily withdrawal limit
…
Variations: The Visa CardHolder does not want a receipt
…
2.2 Withdraw money using a Bank card
Similar to Withdrawal using a Visa card
1. The Bank customer inserts his/her smart card in the ATM’s card reader.
2. The ATM verifies that the card that has been inserted is a smartcard.
3. The ATM asks the Bank customer to enter his/her pin number.
4. The Bank customer enters his/her pin number.
5. The ATM compares the pin number with the one that is encoded on the chip of the smartcard.
6. The ATM requests an authorization from the Bank information system 7. The BankIS confirms its agreement and indicates the daily withdrawal limit.
8. The ATM asks the Bank customer to enter the desired withdrawal amount. Extension point:
verify amount.
9. The Bank customer enters the desired withdrawal amount.
10. The ATM checks the amount against the daily withdrawal limit.
11. The ATM asks the Bank customer if he/she would like a receipt.
12. The Bank customer requests a receipt.
13. The ATM returns the card to the Bank customer.
14. The Bank customer takes his/her card.
15. The ATM issues the banknotes and a receipt.
16.
The Bank customer takes the banknotes and the receipt.3 Use Case Diagram
3.1 Relationships
Complete the Use Case diagram Figure 1. Justify your choice for the best relationship (associations, generalization, include, extend).
VisaCardHolder
Withdraw money with a
Visa card
VisaAS
BankCustomer
BankIS Withdraw
money with a bank card
Consult balance
Deposit money
Deposit cash Deposit checks
Authenticate
Maintenance operator Refill dispenser
Retrieve swallowed cards
Retrieve cheques ATM
Figure 1: ATM Use Case Diagram
3.2 Use Case Specification
Give a textual specification for each use case.
3.3 Papyrus modeling
Use Papyrus to model ATM.
4 Class Diagram
Figure 2: Class diagram of the ATM
Signals are specified by a signal object, whose type represents the kind of message transmitted between objects, and can be dynamically created. The receipt of signals may be bound to activities, state machine transitions, or other behaviors.
5 State machines
CardEntry
PINEntry Verification AmountEntry
ReturningCard abort
/ bank.verifyPIN()
reenterPIN
PINVerify
Counting
Dispensing Giving Money
/ bank.done ATMClass_SM
Figure 3: State machine for class ATM
Idle done
verifyPIN()
VerifyingCard [cardValid] CardValid [else] / atm.abort
VerifyingPIN
entry/ numCorrect=0 PINCorrect
PINIncorrect /atm.PINVerified [else]/cardValid=false;atm.abort
[numIncorrect,maxNumIncorrect] / numIncorrect++;atm.reenterPIN
Verifying BankClass_SM
Figure 4: State machine for class Bank
5.1 Behavior
Justify the state machines in Figure 3 and Figure 4.
Analyze interactions.
Represent some possible interactions with Communication diagrams Represent some possible interactions with Sequence diagrams.
5.2 Modifications
The specification is modified:
• The transaction can be canceled at each instant by depressing a Cancel button.
• After three incorrect PIN code, the card is swallowed by the ATM
Modify the class diagram (add signals), the interaction diagrams, and the state machines to respect the new specification.
5.3 Experimentation
Model the ATM using Papyrus.
